System and method for hermetically sealing a package

ABSTRACT

A method for hermetically sealing a package includes applying a light or energy active resist to a fill port to act as a temporary hermetic seal, patterning the resist, and applying a solder to the fill port, wherein the solder is configured to serve as a hermetic seal.

This application is a divisional of 10/693,213, filed Oct. 23, 2003 nowU.S. Pat. No. 7,276,398, which is hereby incorporated by reference.

BACKGROUND

As integrated circuit (IC) geometries continue to decrease, and with theadvent of Micro-Electro Mechanical Systems (MEMS), the need forreliable, high density packaging solutions increases. A promisingsolution for providing reliable packaging for chips of continuallydecreasing size is Wafer Level Packaging (WLP). WLP is a packagingmethod in which packaging is formed at the wafer level in an IC foundryor other processing location, allowing testing and burn-in to beperformed before the dicing of individual chips.

In certain wafer level packaging (WLP) methods, small cavities orenclosures of an IC or MEMS package may be filled with fluid. In manysuch applications, fluid filling of a WLP may need to be performed insuch a way as to prevent bubbles or gaseous pockets from forming in thefluid filled cavities.

Fluid packaging may perform a number of functions essential for an IC orMEMS device. Packaging may provide electrical connection, electricalisolation or passivation from moisture and electrolytes, physicalisolation from the environment to provide structural integrity ofmechanical devices, thermal and optical protection to preventundesirable performance changes, and chemical isolation to protect fromharsh chemical environments. Electrical connection and isolation mayinclude providing electrical connections from the outside of the MEMSpackage to electrical or mechanical components of the MEMS device insidethe package, electrostatic shielding of the MEMS device, and preventingpenetration of moisture and subsequent corrosion of electricalcomponents or undesired interface adhesion. Mechanical protections mayprovide rigidity allowing mechanical stability throughout the MEMSproduct life- and may also help prevent undesirable interface stressbetween dissimilar materials. If the packaging protection iscompromised, the MEMS device may fail, producing no output for a giveninput or producing invalid or inaccurate output for a given input.

SUMMARY

A method for hermetically sealing a package includes applying a light orenergy active resist to a fill port to act as a temporary hermetic seal,patterning the resist, and applying a solder to the fill port, whereinthe solder is configured to serve as a hermetic seal.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various embodiments of the presentsystem and method and are a part of the specification. The illustratedembodiments are merely examples of the present system and method forcreating a hermetic seal and do not limit the scope thereof. The summaryand other features and aspects of the present system and method willbecome further apparent upon reading the following detailed descriptionand upon reference to the drawings in which:

FIG. 1 is a perspective view of a MEMS package according to oneexemplary embodiment.

FIG. 2 is a cross-sectional view of a MEMS package according to oneexemplary embodiment.

FIG. 3 is a flowchart illustrating a method of creating a hermetic sealfor a MEMS package according to one exemplary embodiment

FIG. 4 is a cross-sectional view of a fluid filled MEMS packageaccording to one exemplary embodiment.

FIG. 5 is a magnified cross-sectional view of a fluid filled MEMSpackage according to one exemplary embodiment.

FIG. 6 is a cross-sectional view of a fluid filled MEMS package afterapplication of a photo resist material according to one exemplaryembodiment.

FIG. 7 is a cross-sectional view of an exposure process according to oneexemplary embodiment.

FIG. 8 is cross-sectional view of a developed photo resist according toone exemplary embodiment.

FIG. 9 is a cross-sectional view of a hermetically sealed MEMS packageaccording to one exemplary embodiment.

FIG. 10 is a simple block diagram illustrating the components of anautomated MEMS packaging system according to one exemplary embodiment.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements.

DETAILED DESCRIPTION

The present specification discloses a system and a method forhermetically sealing a fluid filled integrated circuit (IC) package.More specifically, the present method includes a system and a method forapplying a photo resist material to a fill port as a temporary seal,patterning (i.e., applying, exposing, and developing) the photo resist,and subsequently applying solder to form a permanent hermetic seal overthe fill port. A layer of photo resist may be left between the packagingfluid and the solder in order to insulate the packaging fluid from hot,molten solder during solder application.

As used in this specification and in the appended claims, the term“Micro-Electro Mechanical System” or “MEMS” is meant to be understoodbroadly as describing any very small (micro) mechanical device that maybe constructed on a single semiconductor chip and which may befabricated using integrated circuit (IC) batch-processing techniques.MEMS may be broadly classified as sensors, actuators, a combination ofsensors and actuators, or added circuitry for processing or control.Additionally, a MEMS may include an optical component, making it amicro-electro-optical mechanical system or MEOMS. For the purposes ofpresent specification and appended claims, the term MEMS is meant torefer to any of the above-mentioned classes. The term “package” or“packaging” is meant to be understood as any enclosure or support for aMEMS device providing electrical connection or isolation, andmechanical, thermal, chemical, or optical isolation or passivation inorder to protect the function and prolong the life of the MEMS.

A “fill port” is meant to be understood as any opening in a MEMS packagethat may be used to evacuate the MEMS package of, or fill the MEMSpackage with, a fluid (liquid or gas). Similarly, a “fill port plug” ismeant to be understood as any material configured to function as a seal,either temporarily or permanently, over a fill port. A “hermetic” sealis meant to be understood as any seal which is substantially imperviousto moisture and gases. A “photo resist” is meant to be understood as anyphoto-active polymer or material which may become more or less solublein a particular solvent due to a physical or chemical change afterexposure to light, electromagnetic radiation, or high energy particlebeams. “Exposure” is meant to be understood as a process in which photoresist is selectively exposed to electromagnetic radiation or a particlebeam and subsequently experiences a physical or chemical change. Theterm “development” is meant to be understood as a process in which asolvent or “developer” is introduced to a previously exposed photoresist in order to remove a portion of the photo resist. The term“developer” is meant to denote a solution in which a previously exposedphoto resist may be developed.

In the following specification, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present system and method for creating a hermeticseal to contain a fluid in an IC package. It will be apparent, however,to one skilled in the art, that the present method may also be practicedon any IC either with or without these specific details. Reference inthe specification to “one embodiment” or “an embodiment” means that aparticular feature, structure, or characteristic described in connectionwith the embodiment is included in at least one embodiment. Theappearance of the phrase “in one embodiment” in various places in thespecification are not necessarily all referring to the same embodiment.

Exemplary Structure

According to one exemplary method for IC or MEMS packaging, a fluid isintroduced into the package which may surround portions of mechanical orelectrical devices. This fluid may afterwards be hermetically sealedinside the package. MEMS packaging of this type may include a number ofmethodology design challenges including, but in no way limited to,maintaining a precise amount of packaging fluid in the MEMS package inorder to maintain a given fluid pressure inside the package, making andmaintaining intimate contact between the fill port plug and thepackaging fluid in order to prevent air pockets from forming in thepackaging fluid, using a fill port plug material that is fluid before itcures so that it may flow into the fill port plug geometry, and using afill port plug material which may adhere to gold and other fill portmaterials to form a hermetic seal. Maintaining a given fluid pressureinside the MEMS package may be complicated by a tendency of thepackaging fluid to evaporate before an hermetic seal is in place in thefill port and by a tendency of the packaging fluid to boil whentraditional hermetic seals are applied at a temperature high enough tomake the seal material flow but also high enough to boil the packagingfluid. The present system and method may provide solutions to suchpackaging process design issues.

FIG. 1 illustrates a perspective view of a MEMS package. As shown inFIG. 1, the MEMS package may include an inner enclosure (100) which maysurround a MEMS device or devices. As shown in FIG. 1, the innerenclosure (100) may include a fill port (110) having a fill port channel(120) and a surrounding pad (130). Moreover, the inner enclosure (100)may be surrounded by an outer enclosure (140) and electrical couplingpins (150).

The inner enclosure (100) illustrated in FIG. 1 may be constructed outof silicon, silicon dioxide, glass, gold, or another material. In thecase of a silicon inner enclosure (100), one silicon wafer may be fusedto another silicon wafer with a space hollowed out to fit the MEMSdevice or devices between the silicon wafers. In any case, the innerenclosure (100) may form a hermetic barrier around MEMS devices interiorto it except for an open fill port (110) or fill ports. The fill port(110) may include a fill port channel (120) and a surrounding pad (130)against the surface of which a hermetic seal may later be attached. Thechannel (120) and pad (130) surfaces may be gold or another material.For the purpose of explanation only, the channel (120) and pad (130)surfaces are considered to be gold in the present embodiment, althoughother materials may also be used.

An outer enclosure (140) may also be manufactured to surround a portionof the inner enclosure (100). The outer enclosure (140) may be composedof a ceramic, a plastic, or another material. Electrical connectionsmade to MEMS devices inside the inner enclosure (100) may extend throughthe inner enclosure (100) and outer enclosure (140) to the outside ofthe package and will be referred to as electrical coupling pins (150).The electrical coupling pins (150) are illustrated as being laid out ina dual inline package (DIP), though they may exit the MEMS package inany of a number of configurations (not shown), and may later be used toallow electrical signals to enter and exit the MEMS. In an alternativeMEMS package design, there may be no outer enclosure (140); rather, theMEMS device may be formed directly on a silicon or other type of wafer.

FIG. 2 is a cross-section of a MEMS package illustrating portions of theinner enclosure (100) and outer enclosure (140). As shown in FIG. 2, theinner enclosure (100) includes a fill port (110) having a fill portchannel (120) and a fill port pad (130). A MEMS (200) is shown insidethe package and may be coupled to the packaging at a closer or farthercross-section of the packaging (not shown). The MEMS may also be coupledto package pins (150), though the means of coupling is not shown hereand may take place at closer and/or farther sections of the packaging.As shown in FIG. 2, the fill port (110) provides a fill port channel(120) coupling the MEMS and the inner enclosure (100) to the outsideenvironment. The fill port (110) and its associated fill port channel(120) may be configured to accept and facilitate the filling of theinner enclosure (100) with a filling fluid as will be explained infurther detail below.

Exemplary Implementation and Operation

Turning now to FIG. 3, a flowchart illustrates a method for hermeticallysealing a fluid filled IC or MEMS package according to one exemplaryembodiment. As shown in FIG. 3, the MEMS package sealing process maybegin immediately after a MEMS package has been filled with a degassedpackaging fluid. Such a fluid filled MEMS package may, upon reception ofthe degassed packaging fluid, have a quantity of photo resist applied tothe fill port (step 300). Once the photo resist has been applied, thephoto resist may then be patterned by first exposing it using anappropriate electromagnetic or high energy particle beam and a mask(step 310) and by later developing it in an appropriate developingsolution (step 320). Once the photo resist has been developed, thedeveloping solution may be removed from the packaging and the packagingmay then be prepared for the application of solder (step 330). Onceprepared, solder may be applied in such a way as to make intimatecontact with the fill port surfaces, thereby forming a permanenthermetic seal once the solder cools and cures (step 340). Theabove-mentioned method will now be explained in detail below withreference to FIGS. 4 through 9.

As shown in FIG. 3, the present method for forming a hermetic seal in aMEMS package begins by applying photo resist material to a fill port ofa MEMS packaging enclosure, thereby forming a temporary seal (step 300).While the photo resist material may be applied to the fill port of aMEMS packaging enclosure containing a gas, a liquid, or a vacuum, thepresent exemplary method will be described in the context ofhermetically sealing a fluid filled MEMS packaging enclosure. FIG. 4illustrates a cross-sectional view of a fluid filled MEMS packagingenclosure. As shown in FIG. 4, a fluid (400) may surround a MEMS (200)enclosed by the packaging (100). Additionally, the fluid (400) mayextend into the fill port channel (120). The fluid (400) used to packthe MEMS (200) may be any degassed fluid configured to support eitherthe MEMS (200) or any other micro-electro-optical mechanical system(MEOMS) while reducing the likelihood of contamination. The fluid (400)enclosed in the packaging may be filled to a level lower than or higherthan that illustrated in FIG. 4. Additionally, according to oneexemplary embodiment, the fluid (400) may not extend into the fill portchannel (120) at all. Alternatively, the fluid (400) may extend outsidethe fill port channel (120) and onto the fill port pad (130). For thepurpose of illustration only, the present embodiment is illustratedhaving the fluid (400) at a level extending into, but not beyond thefill port channel (120).

FIG. 5 further illustrates the fluid filled MEMS packaging enclosureaccording to one exemplary embodiment. As shown in FIG. 5, a portion ofthe inner enclosure (100), including a fill port (110) having a fillport channel (120) and a fill port pad (130) may surround and contain aquantity of fluid (400). A portion of the outer enclosure (140) is alsoillustrated. A packaging fluid (400) is illustrated inside the innerenclosure (100) and extending into the fill port channel (120). With theinner enclosure (100) being filled with fluid (400), the present methodmay be performed by first applying photo resist to the fill port of thefilled MEMS packaging (step 300; FIG. 3).

FIG. 6 illustrates a cross-sectional view of a portion of a fluid filledMEMS package after a photo resist (600) has been applied as a temporaryfill port seal (step 300; FIG. 3). As shown in FIG. 6, the photo resist(600) may be applied in such a way as to fill the fill port channel(120) and make intimate contact with the packaging fluid (400) withoutcreating gas pockets between the packaging fluid (400) and the photoresist (600), thereby reducing the likelihood of MEMS damage and/ormalfunction. Once the photo resist (600) fills the fill port channel(120) it adheres to the fill port channel (120) and creates a temporaryhermetic seal. Because the photo resist material (600) flows like anadhesive, it is able to conform to variations in the fill port channel(120) geometry and adheres to the gold surface coating the fill portchannel (120), thereby creating a temporary seal.

FIG. 6 further illustrates that the photo resist (600) may also extendoutside of the fill port channel (120) to form a bead of photo resist(600) common to the fill port pad (130). While FIG. 6 illustrates asingle bead being disposed on top of the fill port pad (130), the photoresist (600) may be applied and spun onto the surface of a single MEMSpackage or an array of packages, substantially covering the uppersurface of the package or packages. Once applied to the fill portchannel (120), the photo resist (600) effectively arrests theevaporation of packaging fluid and forms a temporary seal over the fluidallowing time to pass before downstream processing steps must beperformed.

The photo resist (600) disposed on the fill port channel (120) accordingto the exemplary embodiment illustrated in FIG. 6 may be either apositive photo resist, wherein the exposed region of the photo resistmay become more soluble and may be etched away in a developer while theunexposed regions remain, or a negative photo resist, wherein theexposed region of the photo resist may become resilient to a developerand the unexposed regions may be etched away in a developer. For thepurpose of illustration and ease of explanation only, the followingexemplary embodiment will be described in the context of a positivephoto resist (600), though a negative photo resist is contemplated andmay be used to the same effect by inverting a mask used to exposepositive photo resist (600).

Once the photo resist (600) has been applied to the fill port channel(120) as shown in FIG. 6, the photo resist (600) may be exposed (step310; FIG. 3). FIG. 7 illustrates a cross-sectional view of a quantity ofphoto resist (600) in the process of being exposed (step 310; FIG. 2).As shown in FIG. 7, the photo resist (600) may be exposed by placing anappropriate mask (700) and an energy source (not shown) in opticalcommunication with the photo resist (600). Using any number of speciallydesigned masks (700), the positive photo resist (600) may be exposed insuch a way as to form a ring of unexposed photo resist (740) around thefill port (100; FIG. 5). This ring of unexposed photo resist (740) maybe configured to aid in directing solder into the fill port channel(120) and onto the pad (130). Alternatively, the photo resist may not beexposed at all. Rather, a negative photo resist (600) may be developedso as to remove all of the photo resist (600) except a small quantityconfigured to serve as a temporary seal in the fill port channel (120;FIG. 6).

The mask (700) used to expose the photo resist (600) may include twomaterials, a first material (710) which is transparent toelectromagnetic radiation and a second material (720) which is opaque toelectromagnetic radiation. The mask (700) may be disposed in relativelyclose proximity to the photo resist (600) while disposed at a relativelyfar distance from the energy source (not shown). This configurationproduces, for all practical purposes, a collimated beam or beams ofradiation (730). Once the energy source (not shown) is activated,collimated beams of electromagnetic radiation (730) pass through thetransparent first material (710) of the mask (700). Once the radiation(730) has passed through the first material (710), it is either blockedby the second opaque material (720) of the mask (700) or allowed to passand selectively expose the photo resist (600). Once exposed, the regionsof positive photo resist (600) exposed to the collimated beams ofradiation (730) may undergo a physical or chemical change making themsoluble in the presence of a certain developing solution. In contrast,those areas of positive photo resist (600) left unexposed by virtue ofthe mask (700) may remain resistant or insoluble in the same developingsolution.

The energy source (not shown) may produce electromagnetic radiation or ahigh energy particle beam. For the purpose of illustration only, thepresent system and method will be described in the context of an energysource that produces electromagnetic radiation, though other types ofenergy sources may be used with an appropriate photo resist (600).Alternative techniques for exposing the photo resist (step 310; FIG. 2)may include, but are in no way limited to, photolithography, extremeultraviolet lithography (EUV), or x-ray lithography (XRL) in conjunctionwith an appropriate photo resist or chemical-amplified resist (CAR).According to one exemplary embodiment, an electron resist may be usedand electron-beam lithography may be employed to pattern the electronresist. According to this exemplary embodiment, the electron resist maybe selectively formed using a scattering with an angular limitationprojection electron beam lithography (SCALPEL) system to form atemporary hermetic seal. In another exemplary embodiment, an ion resistmay be used in conjunction with ion-beam lithography to pattern a resistfor use as a temporary hermetic seal. For illustration purposes only, apositive photo resist and a photolithographic technique will bepresented herein.

Additionally, according to one exemplary embodiment, resolutionenhancement techniques may be used in conjunction with the photolithographic process in order to provide better depth of focus andexposure latitude. These resolution enhancement techniques may includethe use of a phase shifting mask (PSM) or a mask with optical proximitycorrection (OPC).

After exposure of the photo resist (step 310; FIG. 3), the photo resistmay be developed in an appropriate developing solution (step 320; FIG.3). In the case of a positive photo resist (600), exposed areas of thephoto resist may become soluble in the developer and may be removed.Conversely, those areas of the photo resist (600) which were not exposedby the energy source (not shown) may be resilient to the developingsolution.

FIG. 8 illustrates a cross-sectional view of a MEMS package after adeveloping process has been performed thereon. As shown in FIG. 8, uponcompletion of a developing process (step 320; FIG. 3), an unexposedphoto resist ring (740) as well as an unexposed photo resist (600) plugmay exist on the package. The previously exposed areas of photo resist(740) yield to dissolution by the developing solution, therebyselectively being removed after the developing process (step 310, FIG.3). In the exemplary embodiment illustrated in FIG. 8, a ring ofunexposed photo resist (740) has been formed in order to aid in a laterprocessing step, namely the application of a solder (step 340; FIG. 3).

Additionally, a quantity of unexposed photo resist (600) may remain inthe fill port channel (120) forming a temporary hermetic seal. Accordingto one exemplary embodiment, the quantity of unexposed photo resist(600) that remains during the developing process is dependant upon thelength of time the photo resist is exposed, the length of time the photoresist is developed, the type of photo resist used, and the developer inwhich the photo resist is developed. The unexposed photo resist (600)that remains in the fill port channel (120) functions as a temporaryhermetic seal to arrest evaporation or other leakage of the packagingfluid (400) from the MEMS package while also protecting the packagingfluid from contamination or heat introduced by solder flux in asubsequent soldering step (step 340; FIG. 3). Unexposed photo resist(600) may also remain on other portions of the MEMS packaging (notshown), depending on developing parameters implemented.

Following the photo resist development (step 320; FIG. 3), developer mayremain on portions of the MEMS package. A developer residue may beremoved by washing the MEMS package in de-ionized water or anotherappropriate solution. Once washed, the washing solution may then beremoved by evaporation, either unassisted or with the aid of a dryingsolvent.

Following developer removal (step 330; FIG. 3), solder may be applied tothe fill port channel (120) to create a permanent hermetic seal. Turningnow to FIG. 9, a hermetic solder seal (900) is shown in the fill port(120) of a MEMS package. After making intimate contact with surfaces ofthe fill port channel (120) and fill port pad (130), the solder (900)may adhere to and form a permanent hermetic seal to the gold and othersurfaces in the fill port channel (120) and/or over the fill port pad(step 340; FIG. 3).

Application of the solder (step 340; FIG. 3) may be performed by firstapplying a solder paste containing flux to improve the wettingcharacteristics of the solder (900) upon re-flow. Once the solder pastehas been applied to the fill port channel and to other locations wherethe solder (900) is desired, the solder may be heated and distributedaccording to a re-flow process. As noted above with reference to FIG. 8,a fill port plug made of unexposed photo resist (600) may remain in thefill port channel (120) providing a barrier between packaging fluid(400) and solder (900) containing solder flux. The barrier of unexposedphoto resist (600) may insulate the packaging fluid from the solderduring solder application. This insulating barrier formed by theunexposed photo resist (600) will prevent solder flux from mixing withthe packaging fluid while simultaneously insulating the packaging fluidfrom higher temperatures attendant to a molten solder. Eliminatingcontamination of the fluid (400) by solder flux prevents damage to theMEMS contained in the MEMS package. Additionally, the insulationprovided by the unexposed photo resist (600) prevents the fluid (400)from being heated to its boiling point, a condition that would createundesirable bubbles to be formed within the fluid (400) as well aschange the fluid pressure thereby damaging the MEMS (200; FIG. 4).Furthermore, the solder (900) used in the present system and method maybe a low temperature solder in order to maintain lower solderapplication temperatures.

Application of the solder (900) may also be facilitated by an unexposedand developed photo resist ring (740) or other developed photo resiststructure. As shown in FIG. 9, the unexposed and developed photo resist(740) may surround a quantity of deposited solder (900) thereby securingits location on the MEMS package. This ring allows the solder (900) tocool and solidify in a stationary condition thereby maintaining contactwith the fill port channel (120) and fill port pad (130). By maintainingcontact with the above-mentioned surfaces, a permanent hermetic seal isproduced by the cooled solder (900).

Although the photo resist (600) fill port plug need not remain once ahermetic solder seal has been formed over the fill port (110), the photoresist (600) fill port plug may be left intact since it may not harm theMEMS and may be difficult to remove once the solder (900) has set.Similar to the photo resist (600) fill port plug, once the permanenthermetic seal is formed by the solder (900), the unexposed photo resistsolder ring (740) may no longer be needed. The unexposed photo resistsolder ring (740) may be left intact or removed by any number ofmechanical or chemical means.

FIG. 10 illustrates an automated embodiment of the present system andmethod. As shown in FIG. 10, an automated system (1000) for hermeticallysealing a MEMS package may include a computing device (1010)communicatively coupled to an energy source (1020), a mask (1030), asoldering device (1040), a resist dispenser (1050), a resist developer(1060), and a solder reflow device (1070). When a request is made tohermetically seal a MEMS package, the computing device (1010) maycontrollably move and operate the coupled devices to perform the methodillustrated in FIG. 3. Additionally the coupled computing device (1010)may be configured to aid in or entirely regulate a decision makingprocess associated with the hermetic sealing of a MEMS package.Moreover, the computing device (1010) may govern robotic arms (1080),conveyer belts (1090), or other means to move, rotate, or otherwisemanipulate the MEMS package, photolithographic masks (1030), energysource (1020), soldering device (1040), resist dispenser (1050), resistdeveloper (1060), and/or solder reflow device (1070) in order to morefully automate the cleaning process. The computing device (1010) mayalso govern the length of time the photo resist is exposed, the lengthof time the photo resist is subsequently developed, as well as the timebetween various steps in the present method. The computing device mayregulate the temperatures of solders and solvents and may directprocessing steps in order to produce MEMS packages according to acertain design or to improve the efficiency of the fabrication process.Such an automated hermetic sealing system may stand alone or beincorporated directly into an IC fabrication or packaging foundry.

In conclusion, the present method for hermetically sealing MEMS packagesmaintains a stable ambient pressure in the packaging fluid while photoresist is applied and patterned as well as while solder is applied,thereby effectively producing a higher yield of working MEMS devices. Bydisposing the photo resist in intimate contact with the packaging fluidand eliminating the formation of bubbles, severe packaging fluidpressure increases may be avoided during solder application as thethermal coefficient for gases is generally much greater than that offluids or solids. Similarly, by leaving a photo resist plug in the fillport channel and in contact with the packaging fluid, the packagingfluid may effectively be insulated from the higher temperatures of themolten solder being applied to the fill port. Finally, using a lowtemperature solder may also decrease the severity of pressurefluctuations in the packaging fluid, thereby lowering the chances ofdamaging MEMS devices being packaged.

Moreover, the sealing process described above allows for the passage oftime between steps. The application of a photo resist material may beperformed immediately after the MEMS packaging enclosure has been filledwith a packaging fluid in order to arrest packaging fluid evaporationand maintain a packaging fluid level. However, once this temporary photoresist seal has been set later processing steps may not need to beperformed immediately, allowing some flexibility in downstreamprocessing. The same may be said after photo resist patterning iscomplete as long as a photo resist plug is left intact in the fill portchannel.

Furthermore, a photo resist fill port plug may serve to prevent solderflux from contaminating the packaging fluid of a MEMS package duringsolder application. This contamination barrier prevents potential damageto a MEMS device that may otherwise occur if solder flux were allowed topenetrate the MEMS package enclosure.

The preceding description has been presented only to illustrate anddescribe exemplary embodiments of the present system and method. It isnot intended to be exhaustive or to limit the system and method to anyprecise form disclosed. Many modifications and variations are possiblein light of the above teaching. It is intended that the scope of thesystem and method be defined by the following claims.

1. An integrated circuit (IC) package, wherein said IC package wasformed by: sealing a fill port with a light or energy active resist;patterning said resist; and hermetically sealing said fill port with asolder; wherein a portion of said resist remains in said IC package. 2.The package of claim 1, wherein: said resist comprises a photo resist;and said patterning said resist comprises a photolithographic process.3. The package of claim 2, wherein said photo resist comprises one of anegative photo resist or a positive photo resist.
 4. The package ofclaim 3, wherein said sealing a fill port with a light or energy activeresist comprises disposing said resist in said fill port such that saidresist is in intimate contact with said packaging fluid.
 5. The packageof claim 4, wherein said photolithographic process removes a portion ofsaid photo resist sufficient to exposes a surface of a fill port channelor a fill port pad; wherein said solder hermetically seals to saidsurface.
 6. The package of claim 1, further comprising: a ring disposedaround said fill port; wherein said ring is exposed resist configured toaid in an application of said solder.
 7. A hermetically sealed packagecomprising: an inner enclosure; a fill port channel coupling said innerenclosure to an atmosphere; a quantity of resist disposed in said fillport channel; and a quantity of solder disposed in said fill portchannel, wherein said quantity of solder hermetically seals said innerenclosure.
 8. The hermetically sealed package of claim 7, furthercomprising a quantity of fluid disposed in said inner enclosure.
 9. Thehermetically sealed package of claim 8, wherein said quantity of resistis configured to insulate said fluid during an application of saidquantity of solder.
 10. The hermetically sealed package of claim 7,further comprising a micro-electro mechanical system (MEMS) or amicro-electro-optical mechanical system (MEOMS) disposed in said innerenclosure.
 11. The hermetically sealed package of claim 7, furthercomprising a ring of resist disposed on said package around said fillport channel; wherein said ring of resist is configured to guide saidquantity of solder into said fill port channel.
 12. The hermeticallysealed package of claim 7, wherein said quantity of resist comprises oneof a negative photo resist or a positive photo resist.
 13. Ahermetically sealed micro-electro mechanical system (MEMS) packagecomprising: an inner enclosure; a MEMS disposed in said inner enclosure;a fill port channel coupling said inner enclosure to an atmosphere; aquantity of resist disposed in said fill port channel; and a quantity ofsolder disposed in said fill port channel, wherein said quantity ofsolder hermetically seals said inner enclosure.
 14. The hermeticallysealed MEMS package of claim 13, further comprising a filling fluiddisposed in said inner enclosure.
 15. A hermetically sealed packagecomprising: a means for enclosing an integrated circuit or a MEMS; ameans for channeling a fluid into said means for enclosing; a quantityof resist disposed in said means for channeling; and a means forhermetically sealing a channel disposed in said means for channeling,wherein said means for hermetically sealing hermetically seals saidmeans for enclosing.
 16. The hermetically sealed package of claim 15,further comprising a quantity of fluid disposed in said means forenclosing an integrated circuit or a MEMS.
 17. The hermetically sealedpackage of claim 16, wherein said quantity of resist is configured toinsulate said fluid during an application of said means for hermeticallysealing.
 18. The hermetically sealed package of claim 15, furthercomprising a micro-electro mechanical system (MEMS) or amicro-electro-optical mechanical system (MEOMS) disposed in said meansfor enclosing.
 19. The hermetically sealed package of claim 15, furthercomprising a ring of resist disposed on said package around said meansfor channeling; wherein said ring of resist is configured to guide saidmeans for hermetically sealing into said means for channeling.
 20. Thehermetically sealed package of claim 15, wherein said quantity of resistcomprises one of a negative photo resist or a positive photo resist. 21.The hermetically sealed package of claim 15, wherein said means forhermetically sealing a channel comprises a quantity of solder.